CVE-2025-21817 block: mark GFP_NOIO around sysfs ->store()
A deadlock in the Linux kernel block layer can cause a denial of service when sysfs store operations trigger memory allocation during queue freeze.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-21817?
CVE-2025-21817 is a medium-severity denial of service vulnerability in Linux kernel, published on 27 Feb 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
block: mark GFP_NOIO around sysfs ->store()
sysfs ->store is called with queue freezed, meantime we have several ->store() callbacks(update_nr_requests, wbt, scheduler) to allocate memory with GFP_KERNEL which may run into direct reclaim code path, then potential deadlock can be caused.
Fix the issue by marking NOIO around sysfs ->store()
Weakness: CWE-667
Which versions are affected by CVE-2025-21817?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-21817?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2025-21817 being exploited?
There is no known exploitation of CVE-2025-21817 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2025-21817, DEBIAN-CVE-2025-21817, GHSA-3f4p-8qj7-5fxp, ROOT-OS-DEBIAN-12-CVE-2025-21817, ROOT-OS-UBUNTU-2204-CVE-2025-21817, ROOT-OS-UBUNTU-2404-CVE-2025-21817 and 1 more.